Electrical plug with detachable cap



Oct, 6, 1959 R. M CUTCHEON 2,907,975

ELECTRICAL PLUG WITH DETACHABLE CAP Filed April 2, 1953 INVENTOR. WCCZ/76fi60/l BY $54 aw fliiorrreys.

fay/Worm I I I United States Patent C 2,907,915 ELECTRICAL PLUG WITH DETACHABLE CAP Raymond'McCuteheon, Chicago, Ill. Application April z, 1953, Nb. 346,319 2 Claims. on. 3393-7196) My invention relates to the type of electric plugs commonly used in homes and other places for the connection of lamps, wires and other appliances to electric current outlets, and the invention is more particularly an improvement upon the Electric Plug patented by me on April 7, 1942, under No. 2,279,173.

In the patented structure, the feature of the invention resided in the connection of the lead wires from the electric supply cord to the prongs of the plug without the need of the usual screws and attaching plates, so that a plug could be assembled with a cord by merely training and clamping such wires in the plug. While the clamping element for the wires in the patented structure involved a block insertible into the plug, it is one object of the improved structure to employ a cap serving the purpose of the block and constituting the forward portion of the plug.

Another object is to design the locking joint for the prongs and cap in a manner to permit the unlocking of the cap by the mere gathering of the prongs, so that the cap may be removed from the base of the plug for the inspection, repair or rewiring of the same.

An important object is to design a cap of the above character which is in a single piece, rendering the cost of the plug economical.

With the above objects in view, a better understand- I ing of the invention may be had by reference to the accompanying drawing, in which- Fig. 1 is a longitudinal, horizontal section of the improved plug on a magnified scale;

Fig. 2 is an end view of the cap alone from the front; and

Fig. 3 is a rear view of the cap portion indicated by the line 33 in Fig. 1.

In accordance with the foregoing, specific reference to the drawing indicates the base of the plug at and the prongs thereof at 11, the rear portions 12 of the prongs being embedded in the base 10 as is the usual practice.

The prongs 11 extend from the base 10 in the parallel courses indicated by full lines in Fig. 1 for proper application to an electric current outlet; and the cap 15 of the plug is primarily formed with a pair of longitudinal bores 17 for the passage of the prongs 11 whenthe cap is to be assembled with the base 10.

The cap 15 is of a form dimensioned to match the base 10; and the capis assembled with the latter by a lap jointed annular formation 19.-

According to conventional design, the plug base 10 is bored axially, as indicated at 20, to provide a passage for the insertion of the sections 21 of the lampor other cord designed to be connected with the plug. However, before the cap 15 is applied to the plug base 10, the protruding portions of the cord sections 21 are extended with their bared terminal wires 24 passing outwardly through slots 25 made in the prongs 11, so that such wires are substantially in the horizontal positions indicated .by' dotted lines in Fig. 1.

When the cord sections 21 have been passed through the plug prongs in the manner just described, the plug ICC shown in Fig. 1, into a constricted portion of the cavity. The outer wall of" the latter is so close to the prong ll'that themo'vement of the cap to join the plug base bend the Wire 24 back against the outer face of the prong, the wire'seatin'gin' a groove 32 in the said outer wall. Thus, the constricted portion 30 of the cavity 22 and the groove 32 will exert a closing pressure on the cord section and bent-over wire with the effect of clamping the latter firmly to the prong 11 and establishing a tight electrical contact between the cord section and the prong.

The joints created between the plug prongs and the cord section in the manner just described are efficient in as shown in'Fig. 1.

principle, but may loosen in case of shock or vibration unless the cap is locked from recession. Means are therefore provided to lock the cap to the plug prongs. Thus, the outer wall of each bore 17 is extended from the rear with an inwardly slanting rib 35 which bears against the related prong 11 on the rearward movement of the cap until the rib snaps halfway into the slot 25 of the prong,

The front end of the slot 25 therefore constitutes a bar to the accidental retraction of the cap from the plug in case of shock or vibration. However, if it is desired to remove the cap from the plug base, it is only necessary to gather the prongs 11 to theextent indicated by finely-dotted lines in Fig. 1. The

Y prongs now clear the ribs 35, permitting the retraction normal or conventional form of the base 10. Further,

the cap 15 is of a form suitable to match'the base and form a lap joint therewith, presenting a smooth external appearance. Further the cap is both an end closure for the plug base and a mounting designed to receive and firmly clamp the wires entering the plug'to the prongs thereof. Further, the locking feature of the cap is accomplishedwithout adding any parts to the same or to the plug base, the slotting of the plug prongs and extension ofthe cap stock with the ribs 35 creating the components of the lock. A' plug is thus formed which not only accomplishes the clamping of the connecting wires as in the patented structure, but also locks the clamping feature positively to the plug base to be proof against accidental loosening or separation. In this manner the components of the plug are permanently locked together and its connections with the cord tightly and electrically maintained.

While I have described the invention along specific lines, various minor changes and refinements may be made therein without departing from its principle, and'I reserve the right to employ all such changes and refinements as may come within the scope and spirit of the appended claims.

I claim:

1. An electric plug comprising a base, a pair of prongs carried by the same and having projecting portions, each of the latter formed with a perforation, the base having a passage for the entrance of a pair of current cord sections with terminal wires engaging 'said portions, a cap having bores for the passage of said portions and the clamping of the wires to them when the cap is assembled with the base; and means carried by the cap to lock the same to the base in such event, said means being ribs extending from the cap into said bores, said ribs being formed to tension the prongs on the movement of the cap and enter said perforations through approxi-' mately half the thickness of the prongs when said assembling is accomplished, and said bores having clearances for the manual flexing of the prongs out of engagement with said ribs to facilitate the unlocking of the cap by reverse movement.

2. An electric plug comprising a base, a pair of prongs carried by the same and having projecting portions, each of the latter formed with a perforation, the base having a passage for the entrance of a pair of current cord sections with terminal wires engaging said portions, a cap having bores for the passage of said portions and the clamping of the wires to them when the cap is assembled with the base, and means carried by the cap to lock the same to the base in such event, said means being ribs extending inwardly the cap into said bores, said ribs being formed to tension the prongs toward each other on the movement of the cap and enter said perforations through approximately half the thickness of the prongs when said assembling is accomplished, and said bores having clearances for the manual flexing of the prongs toward each other out of engagement with said ribs to facilitate the unlocking of the cap by reverse movement.

Refereaces Cited in the file of this patent V UNITED STATES PATENTS Benham Aug. 31, 1954 

